Door hinge and method of manufacturing same

ABSTRACT

A method of manufacturing a door hinge, which can improve productivity by applying both metal injection molding and additive manufacturing is disclosed. The method includes: preparing a first mixture of a first metal powder and a first binder, and a second mixture of a second metal powder and a second binder; molding the first mixture into a first body including a first connection member having a first pinhole; molding the first mixture into a second body including a second connection member having a second pinhole to communicate with the first pinhole; arranging the first body and the second body to align the first pinhole and the second pinhole along an axis to form a cavity; forming a pin member with the second mixture in the cavity by adding up droplets of the second mixture in the cavity; and sintering the first body, the second body, and the pin member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of non-provisional U.S.patent application Ser. No. 16/520,125, filed on Jul. 23, 2019, whichclaims priority to and the benefit of Korean Patent Application No.10-2018-0158660, filed on Dec. 10, 2018, the entire contents of whichare incorporated herein by reference.

FIELD

The present disclosure relates to a door hinge and a method ofmanufacturing the same.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Recently, due to the addition of specifications of convenience, or thelike, the load applied to chassis components is inevitably increased dueto an increase of the weight of a vehicle. Paradoxically, in order toprevent global warming, the world is demanding to improve the fuelefficiency of automobiles to reduce greenhouse gas emissions, andtherefore the need to lighten the weight of automobile parts has beengreatly emphasized.

A door hinge is a part that enables the door to rotate by coupling avehicle body-side bracket and a body-side bracket using a fixing pin. Incase of medium and large vehicles, it is necessary to secure highstrength materials and rigidity due to an increase in the weight of thedoor.

It should be understood that the foregoing description of the backgroundart is merely for the purpose of promoting an understanding of thebackground of the present disclosure, and is not to be construed asadmitting that the present disclosure corresponds to the prior art knownto those skilled in the art.

SUMMARY

One aspect of the present disclosure provides a door hinge and a methodof manufacturing the same, which can improve productivity by applyingboth metal injection molding and additive manufacturing.

In accordance with an aspect of the present disclosure, a door hinge mayinclude: a first body configured to include at least one firstconnection member in which a first pinhole is formed; a second bodyconfigured to include at least one second connection member in which asecond pinhole communicating with the first pinhole is formed; and a pinmember configured to be added and filled in a cavity formed bycommunicating the first pinhole of the first body and the second pinholeof the second body with each other so that the first body and the secondbody are foldably connected to each other.

The first body and the second body may be formed in a metal injectionmolding method, and the pin member may be formed in an additivemanufacturing method.

The first body, the second body, and the pin member may be formed bymolding a mixture of a Fe—Ni—C-based metal powder and a binder, and thensintering the molded mixture.

The first body, the second body, and the pin member may have a tensilestrength of 500 MPa or more and an elongation of 15% or more aftersintering.

The pinhole disposed at the lowermost end, which is either the firstpinhole or the second pinhole, may be closed in a lower end portionthereof.

The pinhole disposed at the lowermost end, which is either the firstpinhole or the second pinhole, may form an enlarged region whose lowerend portion has a larger volume than other regions thereof.

In accordance with another aspect of the present disclosure, a method ofmanufacturing a door hinge may include: a material preparing step ofpreparing a mixture of a metal powder and a binder; a body molding stepof molding a first body including at least one first connection memberin which a first pinhole is formed and a second body including at leastone second connection member in which a second pinhole communicatingwith the first pinhole is formed; a coupling step of coupling the firstbody and the second body to form a cavity in which the first pinhole andthe second pinhole communicate with each other; a pin member moldingstep of molding a pin member by adding the mixture in the cavity formedby communicating the first pinhole and the second pinhole by thecoupling of the first body and the second body and filling the cavitywith the mixture; and a sintering step of sintering the first body, thesecond body, and the pin member.

The body molding step may include molding the first body and the secondbody by molding the mixture in a metal injection molding method, and thepin member molding step may include molding the mixture in an additivemanufacturing method.

The body molding step may include maintaining a temperature of a moldfor molding the first body and the second body at 20 to 40° C., and thepin member molding step may include cooling the mixture while adding themixture on the cavity of which an atmosphere temperature is formed at atemperature corresponding to the temperature of the mold in a state inwhich the temperature of the mixture filled in the cavity is maintainedat 90 to 100° C.

The pin member molding step may include cooling the mixture, which isadded and filled in the cavity, while reaction with oxygen is blocked byinjection of an inert gas.

The method of manufacturing a door hinge may further include: at leastone of a first degreasing step of removing residues from the first bodyand the second body after the body molding step; and a second degreasingstep of removing residues from the first body, the second body, and thepin member after the pin member molding step.

According to embodiments of the present disclosure, since the door hingecan be manufactured by applying both the metal injection molding and theadditive manufacturing, it is possible to omit a post-treatment processsuch as an assembly process and surface processing as in a case ofmanufacturing the door hinge using a typical precision casting method,whereby the number of processes can be reduced compared to the typicalmanufacturing process to improve the productivity.

In addition, it is possible to realize a door hinge having a complicatedshape using the metal injection molding.

On the other hand, compared with a case where the entire door hinge ismanufactured using the additive manufacturing, a pair of bodies having apredetermined shape is manufactured by utilizing metal injectionmolding, and a pin member is formed by utilizing the additivemanufacturing at a main connecting portion, whereby the number ofprocesses can be reduced while maintaining the advantages of eachprocess.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentdisclosure will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a view showing the structure of a general door hinge;

FIG. 2 is a perspective view showing the structure of a door hingeaccording to an embodiment of the present disclosure;

FIG. 3 is an exploded perspective view showing the structure of a doorhinge according to an embodiment of the present disclosure; and

FIG. 4 is a view showing a main process in manufacturing a door hingeaccording to an embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings. The presentdisclosure may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the disclosure to thoseskilled in the art. Like numbers refer to like elements throughout andprime notation is used to indicate similar elements in alternateembodiments.

FIG. 1 is a view showing the structure of an implementation of a doorhinge. As shown in FIG. 1, the door hinge includes a vehicle body-sidebracket 10 fixed to a vehicle body side and a door-side bracket 20coupled to each other using a fixing pin 30 so that the vehiclebody-side bracket 10 and the door-side bracket 20 are foldably orconnected to each other. For engagement with the fixing pin 30, thevehicle body-side bracket 10 and the door-side bracket 20 arerespectively provided with at least one vehicle body-side connectionmember 12 in which a vehicle body-side pinhole 11 is formed, and atleast one door-side connection member 22 in which a door-side pinhole 21is formed. Accordingly, while the vehicle body-side pinhole 11 and thedoor-side pinhole 21 are communicated with each other, the fixing pin isinserted and engaged.

The door hinge illustrated in FIG. 1 is manufactured such that thevehicle body-side bracket 10, the door-side bracket 20, and the fixingpin 30 are respectively molded by precision casting, the fixing pin 30is assembled to the vehicle body-side bracket 10 and the door-sidebracket 20, and then is subjected to a post-treatment process.

Thus, the number of processes increases and the cost of the door hingeincreases. In addition, when the plating of each of the vehiclebody-side bracket 10, the door-side bracket 20, and the fixing pin ispeeled off during the assembling process, quality characteristics may bedeteriorated due to occurrence of corrosion at a corresponding portion.

When manufacturing door hinges, 3D printing technology such as additivemanufacturing may be used. However, when the entire portion of the doorhinge is manufactured using additive manufacturing, it may be difficultto apply the additive manufacturing to mass production due to a lot ofspace and time to be required.

FIG. 2 is a perspective view showing the structure of a door hingeaccording to an embodiment of the present disclosure, FIG. 3 is anexploded perspective view showing the structure of a door hingeaccording to an embodiment of the present disclosure, and FIG. 4 is aview showing a main process in manufacturing a door hinge according toan embodiment of the present disclosure.

As shown in the drawing, a door hinge according to an embodiment of thepresent disclosure includes: a first body 100 configured to include atleast one first connection member 120 in which a first pinhole 110 isformed; a second body 200 configured to include at least one secondconnection member 220 in which a second pinhole 210 communicating withthe first pinhole 110 is formed; and a pin member 300 provided in thefirst pinhole 110 of the first body 100 and the second pinhole 210 ofthe second body 200 so that the first body 100 and the second body 200are foldably connected to each other.

In one implementation of manufacturing door hinges, the pin member 300may be manufactured separately from the first body 100 and the secondbody 200 and assembled to the first body 100 and the second body 200. Inthe present embodiment, however, the pin member 300 is formed in acavity that is formed by the first pinhole 110 of the first body 100 andthe second pinhole 210 of the second body 200 communicating with eachother.

Thus, in this embodiment, it is preferable that the first body 100 andthe second body 200 be molded by metal injection molding (hereinafter,referred to as a MIM method), and the pin member 300 be molded byadditive manufacturing (hereinafter, referred to as an AM method) usinga binder jet technique.

In this embodiment, the shapes of the first body 100 and the second body200 are not limited to a specific shape, but may be variously modifiedin the form of a normal door hinge. However, the first pinhole 110 ofthe first body 100 and the second pinhole 210 of the second body 200 arealigned along an axis to keep in communication with each other so thatthe pin member 300 can form cavities 110 and 210 that can be formed bythe AM method.

In embodiments, droplets of the material for forming the pin member 300are added in the cavities 110 and 210. In one embodiment, in order toapply the AM method to form the pin member 300, it is preferable thatthe lower end portion of the pinhole disposed at the lowermost end,which is either the first pinhole 110 or the second pinhole 210, beclosed. Thus, the lower ends of the cavities 110 and 210 formed by thefirst pinhole 110 and the second pinhole 210 are closed, and a materialused for forming the pin member 300 is added and filled in the closedregion.

Meanwhile, in a case in which the first and second bodies 100 and 200and the pin member 300 are sintered, although the first and secondbodies 100 and 200 and the pin member 300 are contracted at differentcontraction ratios according to sintering conditions, it is preferablethat the pinhole disposed at the lowermost end, which is either thefirst pinhole 110 or the second pinhole 210, form an enlarged region 211whose lower end portion has a larger volume than other regions in orderto prevent the pin member 300 from being detached from the cavities 110and 210 formed by the first pinhole 110 and the second pinhole 210.Thus, an enlarged portion 310 having a larger volume than other portionsof the pin member is formed at the lower end of the pin member.

A method of manufacturing the door hinge according to an embodiment ofthe present disclosure configured as above will be described.

The method of manufacturing the door hinge according to an embodiment ofthe present disclosure includes: a material preparing step of preparinga mixture of a metal powder and a binder; a body molding step of moldingthe first body 100 and the second body 200; a coupling step of couplingthe first body 100 and the second body 200 to form the cavities 110 and210 in which the first pinhole 110 and the second pinhole 210communicate with each other; a pin member molding step of molding thepin member 300 by adding the mixture in the cavities 110 and 210 andfilling the cavities 100 and 210 with the mixture; and a sintering stepof sintering the first body 100, the second body 200, and the pin member300.

The material preparing step is a step of preparing a material used forforming the first body 100, the second body 200, and the pin member 300.In this embodiment, a Fe—Ni—C-based metal powder and a binder are mixedto prepare a mixture.

For example, the Fe—Ni—C-based metal powder is a metal powder obtainedby adding C to a Fe—Ni-based powder in order to secure mechanicalproperties, and Fe-2Ni-0.5C may be used.

As the binder, wax or polyoxymethylene may be used.

As the material used for molding the first body 100, the second body200, and the pin member 300, the Fe—Ni—C-based metal powder of 60 to 65%and the binder of 35 to 40% are mixed in volume % and prepared. Inembodiments, the content of the binder is equal to or more than 35% toavoid insufficient fluidity of the mixture that may cause insufficientfilling of the mixture at the time of injection occurs. The content ofthe binder is equal to or smaller than 40% to reduce a degreasing timeof the binder and avoid or minimize defects caused by a residual binderin the first body 100, the second body 200, and the pin member 300. Thebody molding step is a step of molding and preparing the first body 100including at least one first connection member 120 in which the firstpinhole 110 is formed and the second body 200 including at least onesecond connection member 220 in which the second pinhole 210communicating with the first pinhole 110 is formed, respectively. Eachof the first body 100 and the second body 200 is molded by the MIMmethod using the mixture prepared in the material preparing step.

At this time, it is important to secure the rigidity when the firstconnection member 120 of the first body 100 and the second connectingmember 220 of the second body 200 are coupled to each other. Thus, it ispreferable to secure rigidity of about 7 kgf.

In addition, when the first body 100 and the second body 200 aremanufactured by applying the MIM method, it is important to preventburrs or flashes and weld lines that may occur on the surfaces of thefirst body 100 and the second body 200 and to prevent injection defectsthat may occur in the first body 100 and the second body 200.

Factors preventing the occurrence of such defects include injectionspeed, injection pressure, holding pressure, mold temperature, and thelike, and these factors should be set according to various conditionssuch as the material, shape, and size of a product.

For example, when the injection speed is increased, the filling time isreduced and the injection weight is increased, but burrs and internaldefects may occur. When the injection pressure is increased, the fillingtime is reduced and the injection weight is increased, but a variationfor each filling region may occur.

In addition, when the holding pressure is increased, the injectionweight is increased and the variation for each filling region is small,but weight control is difficult. When the mold temperature is increased,the fluidity of the mixture to be injected can be improved, but bubblesmay be generated on the surface of the product so that the surfacequality may be deteriorated.

Accordingly, in this embodiment, it is preferable to maintain theinjection speed of 60 to 80 cm²/s, the injection pressure of 50 to 70MPa, the holding pressure of 30 to 50 MPa, and the mold temperature of20 to 40° C. as appropriate conditions in the MIM method. By maintainingthe above conditions, it is possible to secure sufficient fluidity ofthe mixture, to remove pores remaining in the interior after injection,and to prevent surface defects.

The coupling step is a step of coupling the first body 100 and thesecond body 200 to form the cavities 110 and 210 in which the firstpinhole 110 and the second pinhole 210 communicate with each other. Thecavities 110 and 210 provide a space where the pin member 300 in whichthe mixture is added and filled is molded.

In the pin member molding step, the pin member is molded in the AMmethod, using the mixture prepared in the material preparing step.

Specifically, the cavities 110 and 210 in which the first pinhole 110and the second pinhole 210 communicate with each other formed bycoupling the first body 100 and the second body 200 in the coupling stepare closed at the lower ends thereof, and a material used for formingthe pin member 300 is added and filled in the closed region. Inparticular, it is preferable that the pinhole disposed at the lowermostend, which is either the first pinhole 110 or the second pinhole 210,form an enlarged region 211 whose lower end portion has a larger volumethan other regions, thereby forming the pin member 300 corresponding tothe shapes of the cavities 110 and 210 in which the enlarged region 211is formed. Thus, the cavities 110 and 210 in which the first pinhole 110and the second pinhole 210 communicate with each other, which are formedby coupling the first body 100 and the second body 200 with each other,may serve as guides for a filling path of an injection means F foradding the mixture for forming the pin member 300.

Meanwhile, in a state in which the temperature of the mixture to befilled in the cavities 110 and 210 is maintained at 90 to 100° C. in thepin member molding step, it is preferable that the mixture be added andcooled while the temperature atmosphere of the cavities 110 and 210 isformed at a temperature corresponding to the mold temperature formolding the first body 100 and the second body 200 in the MIM method.

In particular, when the mixture is injected and added in the cavities110 and 210 to form the pin member 300, in order to maintain thefluidity while maintaining a constant shape, the temperature of a nozzleportion of the injection means F for filling the cavities 110 and 210with the mixture is maintained at 90 to 100° C. and the temperatureatmosphere of the cavities 110 and 210 is maintained at 20 to 40° C.,and preferably at 25 to 35° C. Thus, it is preferable that the mixturewhich is filled and added at 90 to 100° C. be cooled at a temperature of20 to 40° C.

Meanwhile, in the pin member molding step, it is preferable that themixture added and filled in the cavities 110 and 210 be cooled whilereaction with oxygen is blocked by injection of an inert gas such as Argas.

In this manner, the mixture is added in the cavities 110 and 210 formedon the first body 100 and the second body 200, which are separatelymolded, and is cooled. Thus, even when the mixture is bonded to thefirst body 100 and the second body 200 while it is cooled, the bondingforce is insufficient, so that it can be expected that the bondedportion will be removed later at the time of rotation of the first body100 and the second body 200.

In one embodiment, the mixture material for forming the first and secondbodies is the same as that for forming the pin member. In anotherembodiment, the mixture material for forming the first and second bodiesare different from that for forming the pin member such that they havedifferent properties, e.g. contraction ration, from each other.

The sintering step is a step of improving the mechanical properties sothat the first body 100 and the second body 200 manufactured in the MIMmethod and the pin member 300 manufactured in the AM method satisfy thephysical properties required at the door hinge. The sintering step iscarried out by adjusting sintering conditions, for example, a sinteringtemperature and a sintering time.

In this embodiment, it is preferable that the first body 100, the secondbody 200, and the pin member 300 be maintained at the sinteringtemperature of 1350 to 1360° C. for about 1 hour or more to securemechanical properties, so that the tensile strength after sintering is500 MPa or more and the elongation is maintained at 15% or more. Whenthe sintering time has elapsed about 1 hour, a sintered body is smoothlyformed to secure a desired level of mechanical properties.

In particular, in order to prevent surface decarburization of the firstbody 100, the second body 200, and the pin member 300 in the sinteringstep, it is preferable to form the atmosphere inside a sintering furnaceas a weak carbonizing atmosphere. For example, the content of carboninside the sintering furnace is maintained at a level of 0.6% to preventsurface decarburization.

Meanwhile, in the present embodiment, at least one of a first degreasingstep of removing residues from the first body 100 and the second body200 after the body molding step; and a second degreasing step ofremoving residues from the first body 100, the second body 200, and thepin member 300 after the pin member molding step may be furtherperformed.

Preferably, both the first degreasing step and the second degreasingstep are performed, but only the second degreasing step can be performedin order to simplify the number of processes. At this time, the firstdegreasing step and the second degreasing step are carried out at atemperature of about 110 to 130° C., and a degreasing rate of the binderis 90% or more.

Although the present disclosure has been described with reference to theaccompanying drawings and embodiments described above, the presentdisclosure is not limited thereto but is limited by the followingclaims. Accordingly, those skilled in the art will appreciate thatvarious modifications and changes may be made thereto without departingfrom the spirit of the following claims.

What is claimed is:
 1. A method of manufacturing a door hinge,comprising: preparing a first mixture of a first metal powder and afirst binder and a second mixture of a second metal powder and a secondbinder; molding the first mixture into a first body including at leastone first connection member in which a first pinhole is formed; moldingthe first mixture into a second body including at least one secondconnection member in which a second pinhole configured to communicatewith the first pinhole is formed; arranging the first body and thesecond body to align the first pinhole and the second pinhole along anaxis such that the first pinhole and the second pinhole form a cavity;forming a pin member with the second mixture in the cavity by adding updroplets of the second mixture in the cavity; and sintering the firstbody, the second body, and the pin member.
 2. The method ofmanufacturing a door hinge of claim 1, wherein the first body and thesecond body are molded in a metal injection molding method, and whereinthe pin member is formed in an additive manufacturing method.
 3. Themethod of manufacturing a door hinge of claim 1, wherein the first bodyand the second body are molded together in a single mold.
 4. The methodof manufacturing a door hinge of claim 3, wherein a temperature of themold for molding the first body and the second body is maintained at 20°C. to 40° C.
 5. The method of manufacturing a door hinge of claim 1,wherein a temperature of the mold for molding the first body and thesecond body is maintained at 20° C. to 40° C.
 6. The method ofmanufacturing a door hinge of claim 1, wherein forming the pin membercomprises cooling the second mixture while adding up the droplets of thesecond mixture in the cavity of which a temperature is 20° C. to 40° C.,whereas a temperature of the second mixture is maintained at 90° C. to100° C.
 7. The method of manufacturing a door hinge of claim 1, whereinthe pin member is formed while reaction with oxygen is blocked byinjection of an inert gas.
 8. The method of manufacturing a door hingeof claim 1, further comprising: removing residues of the first mixturefrom the first body and the second body after molding the first body andthe second body.
 9. The method of manufacturing a door hinge of claim 1,further comprising: removing residues of the first and second mixturesfrom the first body, the second body, and the pin member after formingthe pin member.
 10. The method of manufacturing a door hinge of claim 1,wherein the second mixture has a contraction ratio greater than that ofthe first mixture during sintering.
 11. The method of manufacturing adoor hinge of claim 1, wherein the first mixture and the second mixtureare the same material.